cifs: Implement netfslib hooks

Provide implementation of the netfslib hooks that will be used by netfslib
to ask cifs to set up and perform operations.  Of particular note are

 (*) cifs_clamp_length() - This is used to negotiate the size of the next
     subrequest in a read request, taking into account the credit available
     and the rsize.  The credits are attached to the subrequest.

 (*) cifs_req_issue_read() - This is used to issue a subrequest that has
     been set up and clamped.

 (*) cifs_prepare_write() - This prepares to fill a subrequest by picking a
     channel, reopening the file and requesting credits so that we can set
     the maximum size of the subrequest and also sets the maximum number of
     segments if we're doing RDMA.

 (*) cifs_issue_write() - This releases any unneeded credits and issues an
     asynchronous data write for the contiguous slice of file covered by
     the subrequest.  This should possibly be folded in to all
     ->async_writev() ops and that called directly.

 (*) cifs_begin_writeback() - This gets the cached writable handle through
     which we do writeback (this does not affect writethrough, unbuffered
     or direct writes).

At this point, cifs is not wired up to actually *use* netfslib; that will
be done in a subsequent patch.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 825e6632ee4f..1121601536d1 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -405,6 +405,9 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	} while (iov_iter_count(iter));
 
 out:
+	if (likely(written) && ctx->ops->post_modify)
+		ctx->ops->post_modify(inode);
+
 	if (unlikely(wreq)) {
 		ret2 = netfs_end_writethrough(wreq, &wbc, writethrough);
 		wbc_detach_inode(&wbc);
@@ -521,6 +524,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 	struct folio *folio = page_folio(vmf->page);
 	struct file *file = vmf->vma->vm_file;
 	struct inode *inode = file_inode(file);
+	struct netfs_inode *ictx = netfs_inode(inode);
 	vm_fault_t ret = VM_FAULT_RETRY;
 	int err;
 
@@ -567,6 +571,8 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 		trace_netfs_folio(folio, netfs_folio_trace_mkwrite);
 	netfs_set_group(folio, netfs_group);
 	file_update_time(file);
+	if (ictx->ops->post_modify)
+		ictx->ops->post_modify(inode);
 	ret = VM_FAULT_LOCKED;
 out:
 	sb_end_pagefault(inode->i_sb);